diff --git a/Framework/Kernel/inc/MantidKernel/Strings.h b/Framework/Kernel/inc/MantidKernel/Strings.h
index 8ae51d40e152b1146ed674024fce08669d1d6b22..a98fc5e178ba860d692e13e22a4cfa9ef662ef47 100644
--- a/Framework/Kernel/inc/MantidKernel/Strings.h
+++ b/Framework/Kernel/inc/MantidKernel/Strings.h
@@ -5,6 +5,7 @@
// Includes
//----------------------------------------------------------------------
#include "MantidKernel/DllConfig.h"
+#include "MantidKernel/MultiThreaded.h"
#include "MantidKernel/StringTokenizer.h"
#include "MantidKernel/System.h"
@@ -56,14 +57,17 @@ namespace Strings {
* For example, join a vector of strings with commas with:
* out = join(v.begin(), v.end(), ", ");
*
+ * This is a simple default version that works in all cases but is potentially
+ * slow.
+ *
* @param begin :: iterator at the start
* @param end :: iterator at the end
* @param separator :: string to append.
* @return
*/
template <typename ITERATOR_TYPE>
-DLLExport std::string join(ITERATOR_TYPE begin, ITERATOR_TYPE end,
- const std::string &separator) {
+DLLExport std::string simpleJoin(ITERATOR_TYPE begin, ITERATOR_TYPE end,
+ const std::string &separator) {
std::ostringstream output;
ITERATOR_TYPE it;
for (it = begin; it != end;) {
@@ -75,6 +79,124 @@ DLLExport std::string join(ITERATOR_TYPE begin, ITERATOR_TYPE end,
return output.str();
}
+//------------------------------------------------------------------------------------------------
+/** Join a set or vector of (something that turns into a string) together
+ * into one string, separated by a string.
+ * Returns an empty string if the range is null.
+ * Does not add the separator after the LAST item.
+ *
+ * For example, join a vector of strings with commas with:
+ * out = join(v.begin(), v.end(), ", ");
+ *
+ * This version is used for random access iterators (e.g. map, set), and
+ * it calls simpleJoin().
+ *
+ * @param begin :: iterator at the start
+ * @param end :: iterator at the end
+ * @param separator :: string to append.
+ * @return
+ */
+template <typename ITERATOR_TYPE>
+DLLExport std::string
+join(ITERATOR_TYPE begin, ITERATOR_TYPE end, const std::string &separator,
+ typename std::enable_if<
+ !(std::is_same<
+ typename std::iterator_traits<ITERATOR_TYPE>::iterator_category,
+ std::random_access_iterator_tag>::value)>::type * = nullptr) {
+ return simpleJoin(begin, end, separator);
+}
+
+//------------------------------------------------------------------------------------------------
+/** Join a set or vector of (something that turns into a string) together
+ * into one string, separated by a string.
+ * Returns an empty string if the range is null.
+ * Does not add the separator after the LAST item.
+ *
+ * For example, join a vector of strings with commas with:
+ * out = join(v.begin(), v.end(), ", ");
+ *
+ * This is a faster threaded version of the join() function above.
+ * It is used only if the iterators are not random access (e.g. vector), as it
+ * needs to be able to determine the distance between begin and end.
+ * It reverts to calling simpleJoin() if the input array is small.
+ *
+ * @param begin :: iterator at the start
+ * @param end :: iterator at the end
+ * @param separator :: string to append.
+ * @return
+ */
+template <typename ITERATOR_TYPE>
+DLLExport std::string
+join(ITERATOR_TYPE begin, ITERATOR_TYPE end, const std::string &separator,
+ typename std::enable_if<
+ (std::is_same<
+ typename std::iterator_traits<ITERATOR_TYPE>::iterator_category,
+ std::random_access_iterator_tag>::value)>::type * = nullptr) {
+
+ // Get max number of threads
+ int nmaxThreads = static_cast<int>(PARALLEL_GET_MAX_THREADS);
+
+ // Define minimum size for using threading
+ int min_size = 500 * nmaxThreads;
+
+ // Get the distance between begining and end
+ int dist = static_cast<int>(std::distance(begin, end));
+
+ if (dist < min_size) {
+
+ // If the input array is small, use the simpler function to avoid
+ // unnecessary overhead from generating the parallel section
+ return simpleJoin(begin, end, separator);
+
+ } else {
+
+ // Allocate vector space
+ std::vector<std::string> output(nmaxThreads);
+ size_t stream_size = 0;
+
+ // Actual number of threads in the current region
+ int nThreads = 1;
+#pragma omp parallel reduction(+ : stream_size)
+ {
+ nThreads = static_cast<int>(PARALLEL_NUMBER_OF_THREADS);
+ int idThread = static_cast<int>(PARALLEL_THREAD_NUMBER);
+ ITERATOR_TYPE it;
+
+ // Initialise ostringstream
+ std::ostringstream thread_stream;
+
+/* To make sure the loop is done in the right order, we use schedule(static).
+
+ From the OpenMP documentation:
+ "When schedule(static, chunk_size) is specified, iterations are divided into
+ chunks of size chunk_size, and the chunks are assigned to the threads in the
+ team in a round-robin fashion **in the order of the thread number**."
+
+ "When no chunk_size is specified, the iteration space is divided into chunks
+ that are approximately equal in size, and at most one chunk is distributed
+ to each thread."
+*/
+#pragma omp for schedule(static)
+ for (int i = 0; i < dist; i++) {
+ thread_stream << separator << *(begin + i);
+ }
+ output[idThread] = thread_stream.str();
+ stream_size += output[idThread].length();
+ }
+
+ // Reserve space in memory for output string
+ std::string master_string = output[0].erase(0, separator.length());
+ master_string.reserve(stream_size - separator.length());
+
+ // Concatenate the contributions from the remaning threads
+ for (int i = 1; i < nThreads; i++) {
+ master_string += output[i];
+ }
+
+ return master_string;
+ }
+}
+
//------------------------------------------------------------------------------------------------
/** Join a set or vector of (something that turns into a string) together
* into one string, separated by a separator,
diff --git a/Framework/Kernel/test/StringsTest.h b/Framework/Kernel/test/StringsTest.h
index f0805ab7127c49d7aea9aacc083e05bc76060851..e65782ae72eb1faaf2fbc04f4846605987818543 100644
--- a/Framework/Kernel/test/StringsTest.h
+++ b/Framework/Kernel/test/StringsTest.h
@@ -267,6 +267,44 @@ public:
TS_ASSERT_EQUALS(out, "Help,Me,I'm,Stuck,Inside,A,Test");
}
+ void test_joinSet() {
+ std::set<std::string> v;
+ std::string out;
+
+ out = join(v.begin(), v.end(), ",");
+ TS_ASSERT_EQUALS(out, "");
+
+ v.insert("Help");
+ v.insert("Me");
+ v.insert("I'm");
+ v.insert("Stuck");
+ v.insert("Inside");
+ v.insert("A");
+ v.insert("Test");
+
+ out = join(v.begin(), v.end(), ",");
+ TS_ASSERT_EQUALS(out, "A,Help,I'm,Inside,Me,Stuck,Test");
+ }
+
+ void test_joinLong() {
+ std::vector<std::string> v;
+ std::string out;
+ std::string ans;
+
+ out = join(v.begin(), v.end(), ",");
+ TS_ASSERT_EQUALS(out, "");
+
+ int n = 100000;
+ for (int i = 0; i < n; i++) {
+ v.emplace_back(std::to_string(i));
+ ans += std::to_string(i) + ",";
+ }
+
+ out = join(v.begin(), v.end(), ",");
+ ans.pop_back();
+ TS_ASSERT_EQUALS(out, ans);
+ }
+
void test_joinCompress() {
std::vector<std::vector<int>> inputList{
@@ -590,4 +628,20 @@ public:
}
};
+class StringsTestPerformance : public CxxTest::TestSuite {
+public:
+ static StringsTestPerformance *createSuite() {
+ return new StringsTestPerformance();
+ }
+ static void destroySuite(StringsTestPerformance *suite) { delete suite; }
+ void setUp() override { input = std::vector<double>(50000000, 0.123456); }
+ void test_join_double() {
+ auto result = join(input.begin(), input.end(), separator);
+ }
+
+private:
+ std::vector<double> input;
+ std::string separator{","};
+};
+
#endif // MANTID_SUPPORTTEST_H_